Planers and sanders are well known in the art and their function in shaping wood to a desired thickness is well known. Blade planers are well known and it is generally accepted that such planers require less power to operate than do belt planers or sanders. It is clear that to achieve double sided planing of the lumber in a single operation, the planer apparatus on each side of the lumber must remove an amount of wood relative to the centerline of the wood. Many centering apparatus have been proposed for use in such planers, but none have been found to be totally satisfactory for use with blade planers. My U.S. Pat. No. 4,417,680 shows an excellent feed mechanism for a belt sander, however, even this apparatus is not completely compatible with a blade planer.
Two problems not present in belt sanders confront the use of a blade planer. First, the cutting action of the blades imparts a discontinuous series of input forces to the lumber which causes oscillation unless the lumber is firmly held in position. Therefore blade planers cannot be mounted in direct opposition as are the belt sanders of my previous invention. Secondly, when lumber which is already very close to or slightly less than the desired thickness is fed into a blade planer apparatus, the staggered configuration of the blade planers requires that the lumber be supported adjacent at least one of the blade planers. Oftentimes this results in the lumber being aligned along one side thereof rather than along the centerline and consequently, with a thin board, one of the blade planers removes an excessive amount of wood thereby reducing the thickness beyond a usable level. For example, a planer may be set to plane boards having a thickness of 15/16ths inches or greater into boards having a thickness of 3/4 inches, with the first blade planer set to remove 1/8 inch and the second set to remove 1/16 inch or vice versa. If a board having a thickness of 13/16" reaches the planer, the first blade planer removes 1/8" resulting in a "scant" board having a thickness of 11/16". Considerable numbers of "scant" boards are produced daily by planers which are incapable of properly centering lumber.